send.c

一个可用的dns服务器源代码

/*
 * ++Copyright++ 1985, 1989
 * -
 * Copyright (c) 1985, 1989
 *    The Regents of the University of California.  All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * 	This product includes software developed by the University of
 * 	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * -
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 * 
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 * -
 * --Copyright--
 */

#ifndef lint
static char sccsid[] = "@(#)send.c	5.18 (Berkeley) 3/2/91";
static char rcsid[] = "$Id: send.c,v 8.2 1997/06/01 20:34:40 vixie Exp $";
#endif /* not lint */

/*
 ******************************************************************************
 *
 *  send.c --
 *
 *	Routine to send request packets to a name server.
 *
 *	Based on "@(#)res_send.c  6.25 (Berkeley) 6/1/90".
 *
 ******************************************************************************
 */


/*
 * Send query to name server and wait for reply.
 */
#ifndef WINNT
#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <netinet/in.h>
#endif 
#include <stdio.h>
#include <errno.h>
#include <nameser.h>
#include <inet.h>
#include <resolv.h>
#include "portability.h"
#include "res.h"

static int s = -1;	/* socket used for communications */


#ifndef FD_SET
#define	NFDBITS		32
#define	FD_SETSIZE	32
#define	FD_SET(n, p)	((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
#define	FD_CLR(n, p)	((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
#define	FD_ISSET(n, p)	((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
#define FD_ZERO(p)	bzero((char *)(p), sizeof(*(p)))
#endif



unsigned short nsport = NAMESERVER_PORT;



/*
 ******************************************************************************
 *
 *   SendRequest --
 *
 *	Sends a request packet to a name server whose address
 *	is specified by the first argument and returns with
 *	the answer packet.
 *
 *  Results:
 *	SUCCESS		- the request was sent and an answer
 *			  was received.
 *	TIME_OUT	- the virtual circuit connection timed-out
 *			  or a reply to a datagram wasn't received.
 *
 *
 ******************************************************************************
 */

int
SendRequest(nsAddrPtr, buf, buflen, answer, anslen, trueLenPtr)
	struct in_addr	*nsAddrPtr;
	char		*buf;
	int		buflen;
	char		*answer;
	u_int		anslen;
	int		*trueLenPtr;
{
	register int n;
	int try, v_circuit, resplen;
	int gotsomewhere = 0, connected = 0;
	int connreset = 0;
	u_short id, len;
	char *cp;
	fd_set dsmask;
	struct timeval timeout;
	HEADER *hp = (HEADER *) buf;
	HEADER *anhp = (HEADER *) answer;
	struct iovec iov[2];
	int terrno = ETIMEDOUT;
	char junk[512];
	struct sockaddr_in sin;

	if (_res.options & RES_DEBUG2) {
	    printf("------------\nSendRequest(), len %d\n", buflen);
	    Print_query(buf, buf+buflen, 1);
	}
	sin.sin_family	= AF_INET;
	sin.sin_port	= htons(nsport);
	sin.sin_addr	= *nsAddrPtr;
	v_circuit = (_res.options & RES_USEVC) || buflen > PACKETSZ;
	id = hp->id;
	/*
	 * Send request, RETRY times, or until successful
	 */
	for (try = 0; try < _res.retry; try++) {
	usevc:
		if (v_circuit) {
			int truncated = 0;

			/*
			 * Use virtual circuit;
			 * at most one attempt per server.
			 */
			try = _res.retry;
			if (s < 0) {
				s = socket(AF_INET, SOCK_STREAM, 0);
				if (s < 0) {
					terrno = errno;
					if (_res.options & RES_DEBUG)
					    perror("socket (vc) failed");
					continue;
				}
				if (connect(s, (struct sockaddr *)&sin,
				   sizeof(struct sockaddr)) < 0) {
					terrno = errno;
					if (_res.options & RES_DEBUG)
					    perror("connect failed");
					(void) close(s);
					s = -1;
					continue;
				}
			}
			/*
			 * Send length & message
			 */
			__putshort(buflen, (u_char *)&len);
			iov[0].iov_base = (caddr_t)&len;
			iov[0].iov_len = INT16SZ;
			iov[1].iov_base = buf;
			iov[1].iov_len = buflen;
			if (writev(s, iov, 2) != INT16SZ + buflen) {
				terrno = errno;
				if (_res.options & RES_DEBUG)
					perror("write failed");
				(void) close(s);
				s = -1;
				continue;
			}
			/*
			 * Receive length & response
			 */
			cp = answer;
			len = INT16SZ;
#ifndef WINNT
			while ((n = read(s, (char *)cp, (int)len)) > 0) {
#else
			while ((n = recv(s, (char *)cp, (int)len,0)) > 0) {
#endif
				cp += n;
				if ((len -= n) <= 0)
					break;
			}
			if (n <= 0) {
				terrno = errno;
				if (_res.options & RES_DEBUG)
					perror("read failed");
				(void) close(s);
				s = -1;
				/*
				 * A long running process might get its TCP
				 * connection reset if the remote server was
				 * restarted.  Requery the server instead of
				 * trying a new one.  When there is only one
				 * server, this means that a query might work
				 * instead of failing.  We only allow one reset
				 * per query to prevent looping.
				 */
				if (terrno == ECONNRESET && !connreset) {
					connreset = 1;
				}
				continue;
			}
			cp = answer;
			if ( (u_int)(resplen = _getshort((u_char*)cp)) > anslen) {
				if (_res.options & RES_DEBUG)
#ifndef GUI
					fprintf(stderr, "response truncated\n");
#else
					fprintf(outputfile, "response truncated\n");
#endif               
				len = anslen;
				truncated = 1;
			} else
				len = resplen;
			while (len != 0 &&
#ifndef WINNT
			   (n = read(s, (char *)cp, (int)len)) > 0) {
#else
			   (n = recv(s, (char *)cp, (int)len,0)) > 0) {
#endif
				cp += n;
				len -= n;
			}
			if (n <= 0) {
				terrno = errno;
				if (_res.options & RES_DEBUG)
					perror("read failed");
				(void) close(s);
				s = -1;
				continue;
			}
			if (truncated) {
				/*
				 * Flush rest of answer
				 * so connection stays in synch.
				 */
				anhp->tc = 1;
				len = resplen - anslen;
				while (len != 0) {
					n = (len > sizeof(junk) ?
					    sizeof(junk) : len);
#ifndef WINNT
					if ((n = read(s, junk, n)) > 0)
#else
					if ((n = recv(s, junk, n,0)) > 0)
#endif
						len -= n;
					else
						break;
				}
			}
		} else {
			/*
			 * Use datagrams.
			 */
			if (s < 0) {
				s = socket(AF_INET, SOCK_DGRAM, 0);
				if (s < 0) {
					terrno = errno;
					if (_res.options & RES_DEBUG)
					    perror("socket (dg) failed");
					continue;
				}
			}
#if BSD >= 43
				if (connected == 0) {
					if (connect(s, (struct sockaddr *)&sin,
					    sizeof(struct sockaddr)) < 0) {
						if (_res.options & RES_DEBUG)
							perror("connect");
						continue;
					}
					connected = 1;
				}
				if (send(s, buf, buflen, 0) != buflen) {
					if (_res.options & RES_DEBUG)
						perror("send");
					continue;
				}
#else /* BSD */
				if (sendto(s, buf, buflen, 0,
					   (struct sockaddr *) &sin,
					   sizeof(sin)) != buflen) {
					if (_res.options & RES_DEBUG)
						perror("sendto");
					continue;
				}
#endif

			/*
			 * Wait for reply
			 */
			timeout.tv_sec = (_res.retrans << try);
			if (timeout.tv_sec <= 0)
				timeout.tv_sec = 1;
			timeout.tv_usec = 0;
wait:
			FD_ZERO(&dsmask);
			FD_SET(s, &dsmask);
			n = select(s+1, &dsmask, (fd_set *)NULL,
				(fd_set *)NULL, &timeout);
			if (n < 0) {
				if (_res.options & RES_DEBUG)
					perror("select");
				continue;
			}
			if (n == 0) {
				/*
				 * timeout
				 */
				if (_res.options & RES_DEBUG)
					printf("timeout (%d secs)\n", 
						timeout.tv_sec);
#if BSD >= 43
				gotsomewhere = 1;
#endif
				continue;
			}
			if ((resplen = recv(s, answer, anslen, 0)) <= 0) {
				if (_res.options & RES_DEBUG)
					perror("recvfrom");
				continue;
			}
			gotsomewhere = 1;
			if (id != anhp->id) {
				/*
				 * response from old query, ignore it
				 */
				if (_res.options & RES_DEBUG2) {
					printf("------------\nOld answer:\n");
					Print_query(answer, answer+resplen, 1);
				}
				goto wait;
			}
			if (!(_res.options & RES_IGNTC) && anhp->tc) {
				/*
				 * get rest of answer;
				 * use TCP with same server.
				 */
				if (_res.options & RES_DEBUG)
#ifndef GUI
					printf("truncated answer\n");
#else
					fprintf(outputfile,"truncated answer\n");
#endif
				(void) close(s);
				s = -1;
				v_circuit = 1;
				goto usevc;
			}
		}
		if (_res.options & RES_DEBUG) {
		    if (_res.options & RES_DEBUG2)
#ifndef GUI
			printf("------------\nGot answer (%d bytes):\n",
			    resplen);
#else
			fprintf(outputfile,"------------\nGot answer (%d bytes):\n",
			    resplen);
#endif
		    else
#ifndef GUI
			printf("------------\nGot answer:\n");
#else
			fprintf(outputfile,"------------\nGot answer:\n");
#endif
		    Print_query(answer, answer+resplen, 1);
		}
		(void) close(s);
		s = -1;
		*trueLenPtr = resplen;
		return (SUCCESS);
	}
	if (s >= 0) {
		(void) close(s);
		s = -1;
	}
	if (v_circuit == 0)
		if (gotsomewhere == 0)
			return NO_RESPONSE;	/* no nameservers found */
		else
			return TIME_OUT;	/* no answer obtained */
	else
		if (errno == ECONNREFUSED)
			return NO_RESPONSE;
		else
			return ERROR;
}

/*
 * This routine is for closing the socket if a virtual circuit is used and
 * the program wants to close it.
 *
 * Called from the interrupt handler.
 */
void
SendRequest_close()
{
	if (s != -1) {
		(void) close(s);
		s = -1;
	}
}